Process and apparatus for compensating the yarn tension difference between two yarns on a spindle drive type winding machine

ABSTRACT

In the spindle drive type winding machine, when yarn tension of one of two side yarns is increased, the compensating of said increased yarn tension can be accomplished by the sequence of braking the spindle firstly by said increased yarn tension so as to reduce the rpm of the spindle, accordingly the dancer arm for the other yarn lowers its position to speed up the electric torque motor and spindle by elevating the voltage via the angular displacement of an operation arm.

1 nited States Patent [191 Toriiet a1.

[111 3,822,832 July 9,1974

PROCESS AND APPARATUS FOR COMPENSATING THE YARN TENSION DIFFERENCE BETWEEN TWO YARNS ON A SPINDLE DRIVE TYPE WINDING MACHINE Inventors: Soichi Torii, 28, Shichiku Kamiumenokicho, Kita-ku, Kyoto-shi, Kyoto; Hideo Yamamoto, 19, Fukakusa Nishiuracho 7-chome, Fushimi-ku, Kyota-shi, Kyoto, both of Japan Filed: Aug. 10, 1972 Appl. No.: 279,454

Foreign Application Priority Data Nov. 27, 1971 Japan 46-111580 us. Cl. 242/45 Int. Cl B65h 59/38 Field of Search 242/45 [56] References Cited UNITED STATES PATENTS 3,350,022 10/1967 Bense 242/45 6/1972 Nakai et a1. 242/45 Primary ExaminerStanley N. Gilreath Attorney, Agent, or FirmRobert E. Burns; Emmanuel J. Lobato; Bruce L. Adams [5 7] ABSTRACT In the spindle drive type winding machine, when yarn tension of one of two side yarns is increased, the compensating of said increased yarn tension can be accomplished by the sequence of braking the spindle firstly by said increased yarn tension so as to reduce 1 the rpm of the spindle, accordingly the dancer arm for the other yarn lowers its position to speed up the electric torque motor and spindle by elevating the voltage via the angular displacement of an operation arm.

16 Claims, 8 Drawing Figures PATENTEDJUL 91974 SHEET 1 [If 6 PATENTEB JUL 9:974

SHEU 3 (IF 6 PAIENTEUJUL QIBM I SHEET S 0F 6 PROCESS AND APPARATUS FOR COMPENSATING THE YARN TENSION DIFFERENCE BETWEEN TWO YARNS ON A SPINDLE DRIVE TYPE WINDING MACHINE The present invention relates to a spindle-drive type winding machine. More particularly it relates to a winding machine for taking-up two yarns onto two packages arranged on a common spindle at a constant linear speed. And more particularly it relates to a tension compensating process and apparatus applicable in the event a tension difference between the two yarns being wound-up is observed.

In practical use, a spindle-drive type yarn winding machine can take up at a constant linear speed yarn, which is delivered from a spinneret or a lid or an extruder, to make a cross-wind type package. In such a winding machine, when an attempt is made to wind two separate yarns onto two bobbins in the form of two separate cross-wind packages mounted on a common spindle, sometimes a tension difference between two yarns can be observed. This tension difference is due to various variations in the conditions of the yarns which result from the preparing process previously applied to each yarn. When such tension difference takes place in the winding conditions, faulty wound packages result. These faults include such defects as formation of nonuniform cross windings, formation of a cob-webbing from the end surface of a package, and poor packages of different hardness.

Many winding apparatuses have been invented with the intention of removing such defects. One type of such winding apparatus, for example, has two separate tension controlling units, each consisting of a dancerroll and a tension spring. Because such tension controlling is a mechanical process, it is inherently incapable of non-defective tension controlling. Such defects will result from the many un-equal operating conditions which can be observed between the two controlling apparatuses. That is, the two control apparatuses are operating with no relation to the operation of the spindle or the traverse motion apparatus directly driven by a single electrical torque motor. Consequently unbalanced controlling conditions exist between the two controlling units.

Another type of conventional winding apparatus has one tension control unit provided with an electrical speed control apparatus, but the other unit is provided with a mechanical control apparatus similar to the above mentioned type. Perfect tension control cannot be expected in this case either. This is due to the fact that for the yarn associated with the electrical speed control apparatus, the whole range of yarn tension control is available because of the apparatus ability to control the rpm of the torque motor according to the variation of the yarn tension; while for the yarn associated with the mechanical speed control apparatus no such tension controlling range can be expected. This latter is true because the control range of a mechanical tension control apparatus is limited by the controlling of the yarn tension via the spring mechanism for a dancer roll, without relation to the rpm of the torque motor.

Thus, different winding conditions occur for two yarns being wound on two cross-wind packages mounted on a common spindle.

The principle object of the present invention is to provide a new process and apparatus for a tension con trol system for a spindle-drive type winding machine for winding continuously advancing strands of yarn, wherein the peripheral speed of the winding package is maintained substantially constant in response to the growth of the winding package, and said speed further is matched to the speed of the yarn being wound in response to the tension therein.

Another object of the present invention is to provide a winding machine for winding continuously advancing strands of yarn, wherein said yarns are maintained under a constant predetermined tension, and with equivalent tension between two yarns at all times during the period of winding.

Another object of the present invention is to provide a winding machine for winding continuously advancing strands of yarn, wherein the tension for each yarn is resumed substantially equivalent and equal to a constant predetermined tension as early as possible in the event a tension difference between two yarns should be observed, by means of a compensating apparatus providing a common single spring and a tensioning member for two separate dancer rolls.

The method of compensating the tension difference between two yarns is accomplished in three steps. In step one, the dancer rolls are commonly affected by a single tension spring via a single common pressing member for both dancing arms. In the second step, the dancer arms of said dancer roll are pivoted onto a common supporting axis which is arranged in parallel to the winding unit. In the third step, a lever for a electrical speed control system, provided just under the dancer arm, is operated by said dancer arm. Thus this process has a very sensitive and steady control operation.

The present invention accordingly comprises an apparatus applicable for any type of winding machine on which two winding packages are turned by a common spindle. This spindle is driven by three phase induction torque motor (hereinafter referred to as an electric torque motor) in variable speed corresponding to the extent of the yarn tension sensed by the related yarn tension sensing apparatus.

A yarn, continually advancing at a substantially constant speed, first runsover a guide roller, then passes under a dancer roller and then is directed upwardly. After running over a second guideroller supported on a fixed axis, said yarn can be guided by the action of the sliding rail of the traversing unit. The yarn is wound onto a package in cross-wind guided by the traverse yam guide which oscillates to and fro within said traversing unit.

The dancer arm with the said dancer roller on its end can be swung downwardly by the force of a spring via a common lever. This lever is arranged on the upper side of two dancer arms, and acts on said arms to push them downward. Such downward swinging movement of said arms can also take place by the force of gravity on the total weight of a dancer unit comprising a dancer roller and an arm assembly. 1

These two forces acting on the dancer units tend to pull the dancer arms downwardly, and can be counterbalanced by the tension forces induced within the running yarns. When the relation between these upward and downward forces acting upon said dancer units in one of equilibrium, the dancer rollers rest on their common supporting axis in the normal position within the horizontal plane. In such a condition, the force of the spring effects both dancer arms commonly and uniformly via the common lever mechanism.

Furthermore, an operation arm, which is always urged upwardly by means of a torsion spring, continuously slightly touches or pushes the dancer arms. If the dancer arms move downward from the normal position, the angular displacement of said operation arm causes the torque motor to increase its running speed via a differential transformer which increases the voltage for any one phase of the torque motor, thus increasing the torque applied to the spindle.

If the tension of either yarn should increase above normal, or above that of the other yarn, the dancer roller associated with the increased yarn tension will be swung up from horizontal. This tendency will continue until a torque equilibrium relation of the yarn tension against the self weight plus the enlarged spring force is reached.

Increased yarn tension acts also upon the surface of the package on which the yarn is wound. That is, the rpm of the spindle directly driven by the torque motor is reduced from normal because said tension acts as a braking action onthe spindle. Thus, the winding speed of the yarn onto said package will be substantially reduced. This means that, the magnitude of the yarn tension will be gradually lowered, and the dancer roller moved downward. This continues untilan equilibrium relation of the yarn tension against the spring force plus the self weight of the roller unit can be maintained.

The speed reduction of the spindle also effects the winding speed of another yarn of normal tension, in that both dancer arms are displaced downward by an equal angular displacement. This lowering movement of the dancer arm associated with the yarn of normal tension results in the operation arm being swung angularly downward. This movement in turn speeds-up the torque motor, and the winding speed is increased until the package resumes its given normal speed. When the winding speed reaches normal, the arrangement of the dancer arms, common lever and operation arm is also normal. That is, the upper surfaces of the dancer arms touch against the underside of the common lever, and the under surfaces of the dancer arms touch the upper surface of the operation arm. This means that the tensions of both yarns are now almost equivalent, and winding with normal tension can continue.

Further features and advantages of the present invention will be made clear from the ensuing description, reference being made to the accompanying drawings, in which:

FIG. 1 is a perspective view of the apparatus of the present invention;

FIG. 2 is the partly sectional plan view of the apparatus of FIG. 1;

FIG. 3 is a partly sectional side view of the apparatus of FIG. 1 showing a view with the yarn tension normal;

FIG. 4 is the same view as that of FIG. 3, but one yarn tension is increased and the other remains normal;

FIG. 5 is the same view as that of FIG. 3, but the spindle speed is reduced due to the brake action of the package induced by the increased yarn tension;

FIGS. 6a, 6b and 60 show the diagrammatic equilibrium relation of three forces which correspond to the states of FIGS. 3, 4 and 5 respectively.

Referring to FIGS. 1 to 5, a basic embodiment of the compensating apparatus for yarn tension difference of the present invention is shown.

Referring to FIGS. 1 through 3. Onto the spindle 18, which is turned directly from the electric torque motor, a pair of packages are mounted so that the respective yarns A and B can be wound on said respective packages. The surface of each said package is always in contact with the surface of a contact roll 13. From this arrangement the cross-wind package can be wound by assistance of the action of a traverse yarn guide 14. Before starting a yarn onto the winding unit, the yarns A and B are guided along their yarn path passing under the sliding bail 15, over the fixed guide roll 12 and under the dancer roll 3 on the dancer arm 2. A common axis 1 is supported by the metal of the bracket 17, and onto it an arm 8 with operation arm 7 is pivotally mounted.

A torsion spring 9 is mounted on one end of the common axis 1. One leg of said spring is secured to the collar 10, fixedly mounted on said axis 1, by inserting said end of the spring into the hole provided on said collar 10. The other leg of said spring is fixed to the bracket 17 in the same manner. The spring force induced from the deflection of the torsion spring 9 can act upon the dancer arm 8 via an operation arm 7 so as to turn said arm 7 upwardly (i.e., turn it counter-clockwise when seen from the open side of the spindle).

When the yarn winding proceeds in a normal condition, the bottom surface of the dancer arm 2a and 2b is in contact with the upper surface of the operation arm 7 by a slight force from the torsion spring 9. The height of the operation arm 7 is substantially the uppermost height which the arm 7 may be swung by said torsion spring 9 against the self-weight of the operation arm assembly.

On the end of the axis 1 a differential transformer 16 is provied. By the assistance of said transformer 16 the rpm of the electric torque motor 19 can be controlled, and increased or decreased according to the angular displacement of the operation arm 7.

A dancer roller unit is pivotally mounted on said common axis 1. It consist of a pair of dancer arms 2a and 2b, a dancer roll 3a or 3b mounted on the top end of each dancer arm, and a mounting element for each arm 2a or 2b respectively. Between said two mounting elements, a lever arm 5 with a lever 4 is pivotally mounted on said common axis 1. The length of said lever 4 extends over both dancer arms 2a and 2b. A tension spring 6 is arranged between a hole provided on the center of said lever 4 and a fixing member on the wall of the bracket 17. The length of the tension spring 6 can be adjusted by means of the adjusting screw 20 and the adjusting nut 21. Thus the required tension force of said spring can be controlled.

The compensating function of the present invention will now be described in detail with reference to FIGS. 1 through 6.

As the first case, in the normal running condition both yarns A and B have a given normal and substantially equal tension. In such a case a pair of dancer arms 2a and 2b are always maintained in their normal or equilibrium position, i.e., almost the horizontal position as shown in FIG. 3. Also, an operation arm 7 is maintained in slight touch-with both dancer arms 2a and 2b. Furthermore, spring forced lever 4 is forced down on said dancer arms 2a and 2b.

The yarn tension of the yarns A and B at their normal condition are designated as T and T respectively, and the torque by said tension T and T as T and T respectively. The force acting upon the lever 4 by means of the spring 6 is designated as P and the torque by said spring force as T,,. The vertical forces induced by the weight of each dancer roll unit or the self weight of each dancing roll unit are designated as W and W respectively, and the torque by said self weight W and W are designated as T and T respectively. Practically, the weight of W is equal to that of W so the relation of T T can be seen. When both dancer rollers 3a and 3b are almost in rest at their normalposition, i.e., no displacement, then the relation of whole torques about the common axis 1 are balanced, i.e., the

. equation is m m TWA wa TP/2 As the second case, if the tension value is increased from T and T to T, and T respectively, but the relation of both tensions remained equal, then both dancer arms 2a and 2b will push the lever 4 upward. The lever arm 5 will accordingly be angularly displaced from its normal about the common axis 1, with an accompanying elongation of the tension spring 6. This means that the spring tension is increased from P to P,. So the equation of torque is then Under such increased tension with respect to yam A and B the winding of the yarn onto the respective package will be continued. Such increased torque value continues until it reaches an extent that the upper swing movement, of the dancer rollers 3a and 3b, is, stopped by contact with the stopper (not shown in drawing). Then the braking action by said imcreased yarn tension begins to effect the rpm of the package arranged on the spingle l8, and the slow down of the rpm of the spindle against the driving of the electric torque motor commences.

The slow down of the rpm of the spindle 18 reduces the winding speed of the yarn. This condition induces the downward displacement of both dancer rollers 3a and 3b, from said upper most position, passing through their normal horizontal position. By the downward movement the torque values of T and T- are reduced to T and T which are rather smaller than T and T In addition to this, the operation arm 7 will be pushed down by the downward displacement of the dancer arm 2a and 2b against the force of the torsion spring 9. This angular displacement of the operation arm 7 effects the differential transformer 16, via said common axis 1, and the rpm of the electric torque motor 18 will-be increased. This rpm increase is followed by an increasing of the torque value by the increased yarn tension. When the yarn tension reaches its given normal value the rpm and torque values stop increasing. The dancer arms 2a and 2b swing back to their normal horizontal position. and normal winding is resumed.

As the third case, if the tension value is decreased from T and T to T and T with the relation of both tensions remaining equal, then both dancer arms 2a and 212 will push the operation arm 7 downward by the action of the tension spring 6. When the equation of T1712 raz X TWA wn m tension T of the yarn B remains unchanged. The lever 4 will then be pushed upwardly by the upward displacement of the dancer arm 2a. However, the position of the dancer arm 2b will remain almost unchanged, but will no longer be touched by the lever 4. The formulas of the torque equation in such a case are as follows: for the dancer arm 2a.

101 TWA m Where T41 TA and Tp Tp for the dancer arm 2b,

( 131 TWA) (TTB TWA TAD/2)- Considering the allowable range of the increased tension values between the normal value, at the horizontal position of a dancer arm, and the critical value, at the critical position where a dancer arm loses contact with the lever 4, the allowable range will be:

for dancer arm 2a,

(TTA TWA TP/2) to (TUA A TA) ii A tP for dancer arm 2b,

( m TWA TP/Z) t0 (TU'A A rs) w)- From this it can be seen that the lever 4 stops touching the dancer arm 2b only when the torque value of TTAI CXCeedS the Value Of Tq' A TA).

If the increasing of the yarn tension T, of the yarn A continues, accompanied by the elongation of the length of the spring 6, then the upward displacement of the dancer arm 20 continues until the equation of T =T +T where P P is satisfied. This relation is shown in FIG. 4. The braking action on the spindle 18 by this increased yarn tension T and the resulting decrease of the speed of the spindle 18, occurs for the same reason as in the second case above.

When this reduction of the speed of the spindle 18 takes place, the resulting lowering displacement of the dancer arms 2a and 2b occurs. During this displacement the dancer arms 2a and 2b maintain their relative displaced relationship and finally reach the position as shown in FIG. 5. It is clear from FIG. 5, that only the displacement of the dancer arm 2b can effect the angular displacement of the operation arm 7. This displacement causes the spindle 18 to increase its speed, via the effect of the differential transformer 18, bythe same sequence as mentioned in the second case above.

The following table shows the relation of force according to the position shown in the respective drawing, and according to the compensating steps of yarn tension. 1

Steps The state of For yarn A For yarn B drawing normal FIG. 3 T, T 1 FIG. 4 T,, T,, 2 FIG. 5 T, T,,, final FIG. 3 T, T

i i otez T T, T, and T TH.

Because of the compensating action of the present invention, accomplished by the sequence mentioned above, if at any time the yarn tension becomes too large, the compensation immediately takes place. While because of the provision of the electric troque motor, which directly drives the spindle 18, the equalization of the yarn tension on both yarns is also accomplished within a very short time. The construction of the apparatus of the present invention is very simple and, furthermore, the compensating operation has a large reliability.

Additionally, because of the construction of the present invention, with one spring and one lever, the force of only a single spring can effect either one or both dancer arms similarly. For the sake of simplicity and understanding, consideration of the efiect of the spring force of the torsion spring 9 acting upon the dancer arm 2a and/or 2b via the operation arm 7 has been neglected. This is because said force is almost negligible at the normal position of the dancer arm, i.e., the horizontal position. Of course, for example, in the state of FIG. 5 the tension of yarn B must be raz wa rs rm where T is an upward torque by means of torsion spring 9.

But this effect will be also quite low, and by no means have any important influence upon the compensating conception but, rather, should act so as to assist said compensation.

What is claimed is:

l. A process for compensating for differences in tension between two running strands on a spindle drive type strand winding machine wherein the strands are concurrently and at equal speed taken up onto separate packages mounted on a common spindle driven for rotation by an electric torque motor, the process comprising, in a sequenced combination: resiliently amplifying an increase in tension of at least one of the two strands applying the strand tensions increase so amplifled to the corresponding package so that the electric torque motor is braked and the speed of the spindle is lowered; lowering by angularly displacing an operation arm guiding the run of each strand as a result of the spindle rotation deceleration and; acclerating the rotation of said electric torque motor in accordance with the degree of the angular displacement of said operation arm.

2. A process of compensating the yarn tension as claimed in claim 1, further comprising the steps of guiding each of the strands on one of two dancer arms each pivotally mounted for angular displacement, and spring biasing both of the dancer arms into an equilibrium position for a desired yarn tension on both strands wherein the spring force opposes movement of the dancer arms in response to an increase in yarn tension; whereby the spring force acts only on the dancer arm that is already in its equilibrium position duringthe step of accelerating the torque of the electric torque motor and furthermore, when both yarns tensions are equally increased in value, said spring force acts upon both dancer arms.

3. A spindle-drive type strand winding machine, for taking up two yarns at a constant linear speed continuously onto two separate packages on a common driving spindle simultaneously, the compensating apparatus comprising, in combination: a spindle with two packages; an electric torque motor for driving the spindle; two dancer rollers; two dancer arms for supporting the two dancer rollers respectively; a lever arm; a lever mounted on the lever arm and engaging said dancer arms from above; at least one spring urging the lever downward; an operation shaft; an operation arm secured on the operation shaft and engaging said dancer arms from underneath; means for maintaining said operation arm and dancer arms in contact; a differential transformer responsive to the angular displacement of said operation shaft to vary the voltage for the torque motor.

4. A compensating apparatus of the yarn tension as claimed in claim 3, wherein, the pair of dancer arms, the lever arm, and an arm connected to the operation arm are coaxially mounted on a common axis.

5. A compensating apparatus of the yarn tension as claimed in claim 4, wherein, the common axis is arranged in parallel to the axis of the winding apparatus.

6. A compensating apparatus of the yarn tension as claimed in claim 3, wherein, the lever extends over a portion of both of the dancer arms.

7. A compensating apparatus of the yarn tension as claimed in claim 6, wherein only one spring is provided for urging the lever arm downward.

8. A compensating apparatus of the yarn tension as claimed in claim 3, further comprising urging means for urging the operation arm to slightly touch the dancer arms at the horizontal position of said dancer arm, wherein the operation arm is almost at its upper-most position of angular displacement.

9. A compensating apparatus of the yarn tension as claimed in claim 8, wherein, said urging means is a spring.

10. A compensating apparatus of the yarn tension as claimed in claim 8, wherein said operation arm extends over a portion of both of the dancer arms.

11. A process for compensating for variations in tension, from a given tension for two strands running concurrently and at equal speeds in a spindle drive type winding apparatus wherein the strands are wound into two separate packages rotably mounted on a common spindle, the process comprising the steps of: guiding each of the strands on one of two dancer arms each pivotally mounted independently for angular displacement in one direction in response to an increase in the tension of the associated strand and for angulardisplacement in the other direction in response to a decrease in the tension of the associated strand; biasing both of the dancer arms into an equilibrium position corresponding to said given tension on both strands wherein the biasing force opposes movement of the dancer arms in response to an increase in tension; decreasing the winding speed of both strands in responseto the angular displacement of at least one of said dancer arms in said one direction thereby decreasing the tension in both strands to angularly displace both of said danger arms an equal distance in said other direction until said one dancer arm is substantially in its equilibrium position and the other dancer arm is angularly displaced in said other direction; and increasing the winding speed of both strands in response to the angular displacement of at least one of the dancer arms in said other direction in proportion to the angular displacement of the. dancer arm angularly displaced in said other direction to increase the tension in both strands to restor both dancer arms into'said equilibrium position.

12. In a spindle drive type winding apparatus for winding two concurrently running strands at equal winding speeds into two separate packages rotatably mounted on a common spindle, a device for compensating for variations in the tension of the two strands from a given tension comprising: means for guiding the two strands including two dancer arms; means pivotally mounting each dancer arm independently for angular displacement in one direction in response to an increase in the tension of the associated strand and for angular displacement in the other direction in response to a decrease in the tension of the associated strand; means biasing both of said dancer arms into an equilibrium position corresponding to said given tension on both strands wherein the biasing force opposes movement of the dancer arms in response to an increase in tension; first means responsive to the angular displacement of at least one of said dancer arms in said one dir'ection for decreasing the winding speed of both strands thereby decreasing the tension in both strands to angularly displace both of said dancer arms an equal distance in said other direction until said one dancer armis substantially in its equilibrium position and the other dancer arm is angularly displaced in said other direction; and second means responsive to the angular displacement of at least one of said dancer arms in said other direction for increasing the winding speed of both strands in proportion to the angular displacement of the dancer arm angularly displaced in said other direction to increase the tension in both strands to restore both dancer arms into said equilibrium portion.

13. In an apparatus according to claim 12, wherein first means comprises a first pivotally mounted lever arm and a first member attached to one end thereof and extending over both dancer arms and wherein said means biasing comprises a spring biasing said first member into contact with said dancer arms.

14. In an apparatus according to claim 13, wherein said second means comprises a second pivotally mounted lever arm and a second member attached to one end thereof and extending below both dancer arms and means biasing said second member into contact with said dancer arms.

15. In an apparatus according to claim 14, wherein said first and second lever arms and said dancer arms are pivotally mounted on a common axis.

16. In apparatus according to claim 12, wherein both of said first and second means are responsive to the angular displacement of either one and both of said dancer arms.

UNITED STATES PAT'EZNVT OFFI E CERTIFICATE OF CORRECTION Patent No. 3 822 832 Dated Jun 9 914 In entor( et a].

It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Cdlumn 7, line 48, efter "strands" insert Signed and sealed this 17th day of: December 1974..

(SEAL) Attest; r

McCOY M. GIBSON JR. I C. MARSHALL DANN Attesting Officer Commissioner of Patents F ORM Pia-1050 (10-69) I USCOMM'fDC 50376-PB9 A U.S. GOVERNMENT PRINTING OFFICE 196B 0-366-88l 

1. A process for compensating for differences in tension between two running strands on a spindle drive type strand winding machine wherein the strands are concurrently and at equal speed taken up onto separate packages mounted on a common spindle driven for rotation by an electric torque motor, the process comprising, in a sequenced combination: resiliently amplifying an increase in tension of at least one of the two strands applying the strand tensions increase so amplified to the corresponding package so that the electric torque motor is braked and the speed of the spindle is lowered; lowering by angularly displacing an operation arm guiding the run of each strand as a result of the spindle rotation deceleration and; acclerating the rotation of said electric torque motor in accordance with the degree of the angular displacement of said operation arm.
 2. A process of compensating the yarn tension as claimed in claim 1, further comprising the steps of guiding each of the strands on one of two dancer arms each pivotally mounted for angular displacement, and spring biasing both of the dancer arms into an equilibrium position for a desired yarn tension on both strands wherein the spring force opposes movement of the dancer arms in response to an increase in yarn tension; whereby the spring force acts only on the dancer arm that is already in its equilibrium position during the step of accelerating the torque of the electric torque motor and furthermore, when both yarns tensions are equally increased in value, said spring force acts upon both dancer arms.
 3. A spindle-drive type strand winding machine, for taking up two yarns at a constant linear speed continuously onto two separate packages on a common driving spindle simultaneously, the compensating apparatus comprising, in combination: a spindle with two packages; an electric torque motor for driving the spindle; two dancer rollers; two dancer arms for supporting the two dancer rollers respectively; a lever arm; a lever mounted on the lever arm and engaging said dancer arms from above; at least one spring urging the lever downward; an operation shaft; an operation arm secured on the operation shaft and engaging said dancer arms from underneath; means for maintaining said operation arm and dancer arms in contact; a differential transformer responsive to the angular displacement of said operation shaft to vary the voltage for the torque motor.
 4. A compensating apparatus of the yarn tension as claimed in claim 3, wherein, the pair of dancer arms, the lever arm, and an arm connected to the operation arm are coaxially mounted on a common axis.
 5. A compensating apparatus of the yarn tension as claimed in claim 4, wherein, the common axis is arranged in parallel to the axis of the winding apparatus.
 6. A compensating apparatus of the yarn tension as claimed in claim 3, wherein, the lever extends over a portion of both of the dancer arms.
 7. A compensating apparatus of the yarn tension as claimed in claim 6, wherein only one spring is provided for urging the lever arm downward.
 8. A compensating apparatus of the yarn tension as claimed in claim 3, further comprising urging means for urging the operation arm to slightly touch the dancer arms at the horizontal position of said dancer arm, wherein the operation arm is almost at its upper-most position of angular displacement.
 9. A compensating apparatus of the yarn tension as claimed in claim 8, wherein, said urging means is a spring.
 10. A compensating apparatus of the yarn tension as claimed in claim 8, wherein said operation arm extends over a portion of both of the dancer arms.
 11. A process for compensating for variations in tension from a given tension for two strands running concurrently and at equal speeds in a spindle drive type winding apparatus wherein the strands are wound into two separate packages rotably mounted on a common spindle, the process comprising the steps of: guiding each of the strands on one of two dancer arms each pivotally mounted independently for angular displacement in one direction in response to an increase in the tension of the associated strand and for angular displacement in the other direction in response to a decrease in the tension of the associated strand; biasing both of the dancer arms into an equilibrium position corresponding to said given tension on both strands wherein the biasing force opposes movement of the dancer arms in response to an increase in tension; decreasing the winding speed of both strands in response to the angular displacement of at Least one of said dancer arms in said one direction thereby decreasing the tension in both strands to angularly displace both of said danger arms an equal distance in said other direction until said one dancer arm is substantially in its equilibrium position and the other dancer arm is angularly displaced in said other direction; and increasing the winding speed of both strands in response to the angular displacement of at least one of the dancer arms in said other direction in proportion to the angular displacement of the dancer arm angularly displaced in said other direction to increase the tension in both strands to restor both dancer arms into said equilibrium position.
 12. In a spindle drive type winding apparatus for winding two concurrently running strands at equal winding speeds into two separate packages rotatably mounted on a common spindle, a device for compensating for variations in the tension of the two strands from a given tension comprising: means for guiding the two strands including two dancer arms; means pivotally mounting each dancer arm independently for angular displacement in one direction in response to an increase in the tension of the associated strand and for angular displacement in the other direction in response to a decrease in the tension of the associated strand; means biasing both of said dancer arms into an equilibrium position corresponding to said given tension on both strands wherein the biasing force opposes movement of the dancer arms in response to an increase in tension; first means responsive to the angular displacement of at least one of said dancer arms in said one direction for decreasing the winding speed of both strands thereby decreasing the tension in both strands to angularly displace both of said dancer arms an equal distance in said other direction until said one dancer arm is substantially in its equilibrium position and the other dancer arm is angularly displaced in said other direction; and second means responsive to the angular displacement of at least one of said dancer arms in said other direction for increasing the winding speed of both strands in proportion to the angular displacement of the dancer arm angularly displaced in said other direction to increase the tension in both strands to restore both dancer arms into said equilibrium portion.
 13. In an apparatus according to claim 12, wherein first means comprises a first pivotally mounted lever arm and a first member attached to one end thereof and extending over both dancer arms and wherein said means biasing comprises a spring biasing said first member into contact with said dancer arms.
 14. In an apparatus according to claim 13, wherein said second means comprises a second pivotally mounted lever arm and a second member attached to one end thereof and extending below both dancer arms and means biasing said second member into contact with said dancer arms.
 15. In an apparatus according to claim 14, wherein said first and second lever arms and said dancer arms are pivotally mounted on a common axis.
 16. In apparatus according to claim 12, wherein both of said first and second means are responsive to the angular displacement of either one and both of said dancer arms. 